The field of the invention is manufacturing semiconductor devices. More specifically, the invention relates to apparatus and methods for processing flat media, typically semiconductor material wafers.
Semiconductor devices, such as microprocessor chips, memory chips, and a large number of other similar devices are generally manufactured from wafers, or thin round disks, of a semiconductor material such as silicon. The wafers undergo a large number of manufacturing steps, including cleaning steps, typically performed by rinsing and drying, as well as other processing steps where various chemicals in the form of liquids and/or gases are applied to the wafers.
Centrifugal processing has been used for many years, to perform certain steps in the manufacturing of semiconductor devices. Centrifugal processing is generally carried out in a centrifugal processor having a rotor for holding the wafers within a process chamber. Spray manifolds spray process liquids or gases onto the wafers. The rotor is rotated at high speed, at certain times during the centrifugal processing. This rotation of the wafers provides more uniform distribution of the process chemicals onto the wafers, as well as removal of liquid chemicals from the wafers, via centrifugal force.
Centrifugal processing may also be used with other devices manufactured from or on a flat substrate. These devices include photomasks and other optical devices, memory disks and media, and similar substrates. These various flat media are collectively referred to here as xe2x80x9csemiconductor wafersxe2x80x9d.
Semiconductor wafers are manufactured in a highly specialized factory or fabrication facility known as a xe2x80x9cfabxe2x80x9d. Due to the extremely high costs of building and operating the fab, manufacturing efficiency or throughput of wafers is very important. As a result, there is a need for machines and methods for providing faster or more efficient wafer processing. In addition, wafer processing in the fab requires use of various chemicals which may be costly to buy, and which require special handling after they have been used. As a result, there is also a need to reduce the amount of process chemicals required in processing semiconductor wafers.
Accordingly, it is an object of the invention to provide improved apparatus and methods for centrifugally processing semiconductor wafers.
To these ends, in a first aspect of the invention, a centrifugal semiconductor wafer processor has a rotor within a process chamber. The rotor is designed to hold two cassettes containing wafers. The rotor has a back or first cassette position, towards the back of the rotor, and a front or second cassette position, towards the front of the rotor. The processing capacity of the centrifugal processor is increased (by a factor of 2), by providing positions in the rotor for two cassettes.
In a second and separate aspect of the invention, the rotor has a pair of spaced apart lower cassette support tubes or rails, and a pair of spaced apart lateral cassette support tubes or rails, attached to a front ring, a center ring, and a back plate. The first or back cassette position, for holding a first cassette, is formed approximately between the back plate and center ring, while the front cassette position, for holding a second cassette, is generally formed between the center ring and front ring. The lower cassette support tubes preferably extend continuously from the front ring to the back plate. A first cassette is loaded into the rotor and moved towards the back of the rotor until the first cassette contacts a stopping surface. The front or second cassette is then loaded into the rotor and moved toward the back of the rotor until the front cassette contacts the back of the first cassette. As a result, the centrifugal processor can hold and process an increased number of wafers, within a single processing cycle.
In a third and separate aspect of the invention, the lower cassette support tubes support lower sidewalls of the cassettes. The lateral cassette support tubes preferably support an upper surface of the cassettes, so that the cassettes are secured into position within the rotor. The cassettes can be quickly and easily loaded into and removed from the rotor. The cassettes are secured into position within the rotor by the support tubes, without any need for moving, securing or supporting components.
A centrifugal processor holding three or more cassettes may also be achieved using the inventive principles described.
The invention resides in the described features, as well as in subcombinations of those features. Other objects and advantages will appear below.